Yarra system

The Yarra River flows west from the Yarra Ranges upstream of Warburton, through the Yarra Valley and then opens out into a wider plain as it meanders through the suburbs and city of Melbourne before entering Port Phillip Bay. The Upper Yarra Reservoir, O'Shannassy Reservoir and Maroondah Reservoir harvest water from headwater tributaries and a pump station at Yering is used to divert water from the Yarra River to Sugarloaf Reservoir.

The Yarra River and its tributaries continue to be an important place for Traditional Owners and their Nations. The Wurundjeri Land and Compensation Cultural Heritage Council Aboriginal Corporation is the Registered Aboriginal Party (RAP) for much of the region. Melbourne Water and the VEWH are continuing to work with the RAP to understand how management of water for the environment in the Yarra River can better support Aboriginal aspirations through a joint cultural values mapping project.

In September, landmark legislation protecting the Yarra River — the Yarra River Protection (Wilip-gin Birrarung murron) Act 2017 — passed the Victorian Parliament. It identifies the Yarra River and the many hundreds of parcels of land it flows through as one living, integrated, natural entity. It combines the wisdom of Traditional Owners with modern river management expertise. The Act gives an independent voice to the river by way of the Birrarung Council, a statutory advisory body which must have at least two Traditional Owner representatives on it.

System map

Grey river reaches have been included for context. The numbered reaches indicate where relevant environmental flow studies have been undertaken. Coloured reaches can receive environmental water.

Environmental watering objectives in the Yarra River

Increase, strengthen and maintain plant life on the riverbank and in the channel, as well as on the upper Yarra floodplain and in the billabongs along the river

Protect and increase populations of native fish including threatened species (such as the Australian grayling, Macquarie perch and river blackfish)

Maintain the form of the riverbank and bed Scour silt build-up and clean cobbles in the river to ensure fish, platypus and other water animals have access to healthy habitat pools and places to feed, spawn and shelter

Protect and increase communities of waterbugs, which break down dead organic matter and support the river’s food chain

Improve water quality in river pools, ensuring adequate dissolved oxygen concentrations in the water to support fish, crustaceans and waterbugs

Environmental values

The upper Yarra River (reaches 1–3) provides habitat for a range of native fish species including the river blackfish, spotted galaxias and common galaxias, and contains good-quality riparian and aquatic vegetation. The lower river (reaches 4–6) flows through forested gorges, cleared floodplains and some highly-urbanised areas, and supports several populations of native fish including Australian grayling, river blackfish, Macquarie perch and tupong.

Macquarie perch were introduced to the Yarra River last century and the population is now considered one of the largest and most important in Victoria.

Billabongs are an important feature of the Yarra River floodplain between Millgrove and Yering Gorge as well as of the reach around Banyule Flats near Heidelberg. The billabongs support distinct vegetation communities, and they provide foraging and breeding habitat for waterbirds and frogs. Except in very high flows, most billabongs are disconnected from the Yarra River.

Social and economic values

The upper reaches of the Yarra River provide 70 percent of Melbourne's drinking water. The river also provides social and recreational opportunities for the more than four million people who live in the greater Melbourne area. Swimming and kayaking are popular in some sections, and many sections have aesthetic appeal for walkers and cyclists. The Yarra River corridor supports more than 2,450 ha of urban parklands and public open space that are valued by communities for their tree-dominated landscapes and views of and access to the river. Private tourism and recreation industries also make use of the corridor; for example, there are more than 10 golf courses along the river's length.

Conditions 2018

The Yarra River catchment experienced dry conditions at the start of the 2017–18 water year and water for the environment was used to meet winter baseflow objectives. Higher-than-average rainfall in August 2017 saw the river transition towards an average climate scenario by September 2017, which was then maintained for the remainder of the water year (to June 2018). As a result, many of the minimum environmental flow recommendations were met naturally throughout the main stem of the Yarra during the spring and early summer months.

Water for the environment was used to deliver a high flow in spring to trigger Australian grayling migration back up the system and to scour sediments in the mid-reaches to improve spawning habitat for Macquarie perch. Summer freshes were also delivered along the river to maintain habitat for macroinvertebrates, allow fish movement and improve water quality.

Bolin Bolin and Yering Backswamp billabongs received water for the environment in spring, and frogs were quick to respond as evidenced by an increase in the number of species detected. This was followed by natural filling of Spadonis and Bolin Bolin billabongs from a large storm in early December 2017.

The 2017–18 water year was the first time that Bolin Bolin Billabong received water for the environment. Watering was endorsed by the Wurundjeri Traditional Owners, who have strong cultural connections to the billabong. Data collected during the watering, as well as the existing knowledge held by the Wurundjeri Land and Compensation Cultural Heritage Council Aboriginal Corporation and the experiences of being on Country as part of the monitoring for Bolin Bolin will inform future management objectives and practices.

Scope of environmental watering

Table 1 Potential
environmental watering actions and objectives for the Yarra system

Year-round low flows2 (varying rates from 10– >350 ML/day)

Maintain access to riffle and pool habitat for waterbugs and fish

Allow the riverbank vegetation to dry

Limit the growth of fringing/riparian/terrestrial vegetation into thestream channel

Maintain and/or rehabilitate in-stream vegetation

Summer/autumn freshes (1–4 freshes of varying rates between 60–750 ML/day for 2–4 days each in December–May)

Support native vegetation and improve habitat availability for wetland plants and animals

Spring high flow (1 high flow of 700–2,500 ML/day for 14 days in September– November)3

Promote spawning and migration of native fish species

Maintain channel form

1 The magnitude and duration of potential environmental watering depends on the reach being targeted, with the lower range generally applying to the upper reaches (for example, reach 1) and higher range applying to the lower reaches (for example, reach 6).

2 Low flows are generally provided by passing flows under the environmental entitlement, but during dry conditions, it may be necessary to supplement low flows using managed water for the environment.

3 A spring high flow will only be achieved with significant unregulated flow due to release constraints in the upper reaches of the system. Ceasing harvest at Yering during a natural high flow may help meet the desired flow target in reaches 5 and 6.

Risk management

In preparing its seasonal watering proposal, Melbourne
Water considered and assessed the risks of environmental
watering and identified mitigation strategies. Program
partners continually reassess risks and mitigation actions
throughout the water year

Engagement

Table 2 shows the partners and stakeholder organisations with which Melbourne Water engaged when preparing the Yarra system seasonal watering proposal.

Seasonal watering proposals are informed by longer-term regional catchment strategies, regional waterway strategies, environmental flow studies, water management plans and other studies. These incorporate a range of environmental, cultural, social and economic perspectives and longerterm integrated catchment and waterway management objectives. For further details, refer to the Port Phillip and Western Port Regional Catchment Strategy and Melbourne Water's Healthy Waterways Strategy.